P-126 - Microgravity-Induced attenuation of plant immune response against Pseudomonas syringae

Microgravity poses a significant challenge for plant cultivation and disease management in space. Although previous studies reported enhanced plant susceptibility to microbial pathogens under microgravity conditions, the underlying molecular mechanisms remain unclear. This study investigated how microgravity influences plant immune responses by analyzing disease severity in Arabidopsis and cucumber plants inoculated with the bacterial pathogen Pseudomonas syringae pathovars. Under microgravity conditions, both Arabidopsis and cucumber exhibited significantly increased disease symptoms. However, Arabidopsis pgm-1 mutants impaired in gravity perception showed notably reduced susceptibility. This result suggests that impaired gravity perception under microgravity negatively regulates plant immune responses. Transcriptomic and proteomic analyses revealed marked suppression of immune response and photosynthesis-related genes with a pronounced inhibition of salicylic acid (SA)-mediated signaling pathways. Application of benzothiadiazole (BTH), an activator of the SA pathway, effectively restored plant immune responses and reduced disease symptoms caused by P. syringae pathovars under microgravity conditions. Collectively, this study provides novel insights into the molecular basis of microgravity-induced suppression of plant immunity and highlights BTH as a promising strategy to enhance plant disease resistance in space environments.